It is known generally to provide a damping system in roll paper towel dispensers to absorb the shock that occurs when roll overspin slack is taken up, thereby preventing “tabbing” during use of the dispenser.
Tabbing occurs when a piece of towel tears off the sheet when a user grasps and pulls the paper. Tabbing may occur with one or two hand pulls. Papers that absorb water at the greatest rate are most likely to tab. The rate of water absorbency varies by paper manufacturer and grade. Premium grade papers tend to absorb water the quickest and are generally harder to cut which leads to a higher rate of tabbing.
Tabbing takes place when overspin slack is taken up. A “shock” is present at the moment the overspin slack is exhausted. The shock occurs because the stationary roll towel must begin rotating at the moment the overspin slack is exhausted. The shock is greatest with full rolls and diminishes as the roll is exhausted.
U.S. Pat. No. 7,500,420, issued Mar. 10, 2009, discloses dispenser apparatus for dispensing paper toweling that includes structure for damping forces applied to a roll of paper toweling when overspin slack is taken up and wherein the timing of a cutter blade incorporated in the dispenser apparatus is modified to reduce peak pull force during dispensing. A biased damping roller is displaceable by the toweling when the toweling is pulled to take up the slack and maintain the toweling in taut condition between the end being pulled and the roll.
Paper companies continue to introduce bigger, heavier rolls with smaller core diameters and in some cases proprietary roll support plugs. Paper companies, for example, currently are making paper toweling rolls 10 inches in diameter and having 1,500 feet of paper.
This creates an even greater challenge when dealing with overspin. The biased damping roller approach disclosed in U.S. Pat. No. 7,500,420 may not be adequate to effectively control overspin in certain bigger, heavier rolls.
Overspin can create the following negative dispensing issues for dispensers including self cutting mechanisms, such as drum mounted tear blade systems, an example of which is disclosed in U.S. Pat. No. 7,500,420.
Among the problems is double sheeting. This can happen in two ways. One, on fast pulls the drum can over-rotate, dispensing the next sheet still attached to the first.
Two, the overspun toweling has no tension against the tear blade, which can reduce cutting effectiveness.
Another problem is the tabbing discussed above caused by the shock force created to get the roll spinning.